1. Field of the Invention
The present invention relates to psychometric, neuropsychological, and neurophysiological tests for measuring mental function and more particularly to the use of electroencephalogram (EEG) recordings for such measurements.
2. Description of the Related Art
There is currently no method that efficiently and objectively measures an individual's fundamental cognitive brain functions (“neurocognitive functions”). Neither is there a method that is able to do so on repeated occasions in order to measure changes in fundamental neurocognitive functions due to disease, injury, or other conditions affecting higher cognitive brain functions, or such fluctuating changes due to ongoing remedial treatment.
The presently available various psychometric tests of cognitive function, such as the Wechsler Adult Intelligence Scale (WAIS), each suffer from one or more deficiencies. These deficiencies include cultural bias, subjective interpretation, excessive test length, cumbersome retesting, high cost, and lack of assessment of the subject's motivational factors in performing the test. In addition, most test instruments lack multiple applications of the test that would be needed for repeated testing. There are also a number of ad-hoc computerized cognitive test batteries, such as CANTAB, that use a mix of tasks derived from laboratory research and clinical neuropsychological practice and that ameliorate some of these shortcomings. However, no psychometric test or cognitive test battery provides direct information about the subject's actual brain function and hence supplies no information relative to the putative pharmacological action of a drug, disease, injury or therapy which is being studied or evaluated. This lack of suitable tests is a major barrier to long-term assessment of changes in an individual's fundamental neurocognitive functions. This assessment is of paramount importance in evaluating the success of a putative treatment for any form of condition affecting higher cognitive brain functions, for example drugs to aid memory in elderly patients. In principle direct measurement of brain functions underlying cognitive functions, by EEG measurements of brain wave activity, could overcome these deficiencies. Prior attempts at such EEG measurements, however, have not been fruitful because of one or more major shortcomings. First, there was often a failure to measure brain activity while the subject performed a task taxing the subject's fundamental mental processes, such as attention, memory, and language. Merely recording brain activity while the subject sits idly, watching a meaningless flashing light, or performing a task not requiring her or his full attention is often insufficient to produce patterns of brain activity characterizing individual differences in neurocognitive functioning, or changes in an individual's neurocognitive functions over time. Second, there was most often a reliance on single measures of brain function, such as EEG alpha band power or P300 evoked potential amplitude, that by themselves are insufficient to adequately characterize individual differences in fundamental neurocognitive functions or changes in an individual's fundamental neurocognitive functions due to a disease, its treatment, or other causes. Third, prior brain function studies did not combine measures of task performance with brain function measures in the same mathematical function to characterize individual differences in fundamental neurocognitive functions or changes in an individual's fundamental neurocognitive functions due to a disease, its treatment, or other causes. Similarly, studies using other methods of measuring brain function, such as positron emission tomography or functional magnetic resonance imaging, have not combined measures of task performance with brain function measures in a mathematical function to characterize individual differences in fundamental neurocognitive functions or changes in an individual's fundamental neurocognitive functions due to a disease, its treatment, or other causes.
In Schmidt et al., U.S. Pat. No. 5,339,826, the effectiveness of video-taped training material is tested using EEG. In one method, the student's brain wave alpha and beta band activity is analyzed to determine attention and cognitive activity. In another method, EP (Evoked Potential) responses are measured using multiple-choice questions.
In Cohen U.S. Pat. No. 4,203,452, a single channel of EEG is measured in an attempt to ascertain if a student is undergoing short-term learning or long-term learning.
In Gevins U.S. Pat. No. 5,447,166, EEG signals are used to alter a computer program, i.e. present more or less difficult test material to the user.
Bennett U.S. Pat. No. 3,809,069 seeks to measure the intelligence of a subject using pulsed stimuli to evoke the subject's responses, which are compared to the frequencies of responses of others.
Other possibly relevant patents are U.S. Pat. Nos. 5,991,581; 6,087,090; 6,159,014; 6,280,198 and 6,309,361.
These patents, and the other references cited, are incorporated by reference herein.